Nadine Marguerit De Courtenay

Systems of units still fail to attract the philosophical attention they deserve, but this could change with the current reform of the International System of Units. Most of the SI base units will henceforth be based on certain laws of nature and a choice of fundamental constants whose values will be frozen. The theoretical, experimental and institutional work required to implement the reform highlights the entanglement of scientific, technological and social features in scientific enterprise, while it also invites a philosophical inquiry that promises to overcome the tensions that have long obstructed science studies.

The guest editors would like to thank the University of Paris and the ENSA Paris-Val de Seine for having provided premises to successfully host the 2018 "Measurement at the Crossroads" conference in Paris.Our thanks extend to our funding sources: the conference was made possible thanks to the generous support of the Institut Humanités, Sciences et Sociétés, the SPHERE laboratory and the Laboratoire Matériaux et Phénomènes Quantiques of the University of Paris, the department of History and Philosophy of Science of the University of Paris, the Laboratoire National de métrologie et d'Essais, and the University of Geneva.We would like to thank the many people who contributed to the organization of...

Two complementary debates of the turn of the nineteenth and twentieth century are examined here: the debate on the legitimacy of hypotheses in the natural sciences and the debate on intentionality and ‘representations without object’ in philosophy. Both are shown to rest on two core issues: the attitude of the subject and the mode of presentation chosen to display a domain of phenomena. An orientation other than the one which contributed to shape twentieth-century philosophy of science is explored through the analysis of the role given to assumptions in Boltzmann’s research strategy, where assumptions are contrasted to hypotheses, axioms, and principles, and in Meinong’s criticism of the privileged status attributed to representations in mental activities. Boltzmann’s computational style in mathematics and Meinong’s criticism of the confusion between representation and judgment give prominence to an indirect mode of presentation, adopted in a state of suspended belief which is characteristic of assumptions and which enables one to grasp objects that cannot be reached through direct representation or even analogies. The discussion shows how assumptions and the movement to fiction can be essential steps in the quest for objectivity. The conclusion restates the issues of the two debates in a contemporary perspective and shows how recent developments in philosophy of science and philosophy of language and mind can be brought together by arguing for a twofold conception of reference.Keywords: Assumption; Hypothesis; Description; Mode of presentation; Ludwig Boltzmann; Alexius Meinong.

The philosophical significance attached to the construction of systems of units has traditionally been confined to the notion of convention, while their adoption was considered to be the exclusive province of the history and sociology of science. Against this tradition, a close articulation between history, philosophy, and sociology of science is needed in order to analyse the recent reform of the International system of units. In the new SI, units are redefined on the basis of certain fundamental constants of nature, established by physical theories, whose values are fixed without uncertainty. The purpose of this article is to show that the redefinition of SI units, far from being a convention, involves a holistic reconstruction of our concepts of quantities from accepted theoretical laws. Fixing the values of the defining constants stabilizes these laws within the framework of physics through a twofold adjustment procedure that ensures both a semantic coordination between theory and world and an intersubjective coordination between human agents required by social activities. This double adjustment implies a treatment of uncertainties that results in closely entwining the pursuit of truth as correspondence and truth as coherence which turn out to be complementary, thus highlighting the anthropological underpinnings of scientific realism.

The way metrologists conceive of measurement has undergone a major shift in the last two decades. This shift can in great part be traced to a change in the statistical methods used to deal with the expression of measurement results, and, more particularly, with the calculation of measurement uncertainties. Indeed, as we show, the incapacity of the frequentist approach to the calculus of uncertainty to deal with systematic errors has prompted the replacement of the customary frequentist methods by fully Bayesian procedures. The epistemological ramifications of the Bayesian approach merge with a deep empiricist mood tantamount to an “epistemic turn”: measurement results are analysed in terms of degrees of belief, and central concepts such as error and accuracy are called into question. We challenge the perspective entailed by this epistemic turn: we insist on the centrality of the concepts of error and accuracy by underlining the intentional character of measurement that is intimately linked to the process of correction of experimental data. We further circumvent the difficulties posed by the classical analysis of measurement by stressing the social rather than the epistemic dimension of measurement activities.

During the mathematics lesson dealing with imaginary numbers, Törless, the young hero of Robert Musil’s novel, The Confusion of Young Törless, is truly amazed. Imaginary numbers are impossible: numbers which, put to the square, give a negative number cannot exist. Still, these imaginary numbers seem to be used to reach quite definite and concrete results. This looks to Törless as if mathematics could make you walk steadily on a bridge which had only a beginning and an end and nothing in between, as if the bridge were complete